1. Field of Invention
The present invention relates to a DPSS laser, and more particularly to a green DPSS laser wherein a volume and a weight thereof are significantly reduced with respect to conventional ones.
2. Description of Related Arts
Diode Pumped Solid State (DPSS) lasers have got increasingly popularly used due to their energy efficiency, high reliability, ruggedness, internal blanking and low Total Cost of Ownership (TCO). Their example applications include laser pointer, machining, material processing, spectroscopy, wafer inspection, light show, medical diagnostics and etc.
A typical green DPSS laser is as schematically shown in FIGS. 1A and 1B. The green DPSS laser consists of a laser diode (LD) that comprises a LD casing 101, a heat sink mounted within the LD casing 101, a semiconductor chip 102 mounted on the heat sink and an output window, which emitting a pumping radiation for exciting a lasing medium. A lens system 103 is mounted within a casing 106 for focusing of the pumping radiation. An optical resonant cavity, which is mounted within a cavity casing 108, includes a lasing medium 104 for a light amplication of 1064 nm in wavelength and an intracavity frequency doubler 105 for converting 1064 nm to 532 nm in wavelength, wherein the lasing medium 104 and the intracavity frequency doubler are separated with each other or being combined together. In other words, the LD casing 101, the lens system casing 106 and the cavity casing 108 are sealed in the casing 109. If the lasing medium 104 and the intracavity frequency doubler 105 are combined together, an anti-reflection coating at 808 nm (AR@808 nm) and a high-reflection coating at 532 nm (HR@532 nm) and 1064 nm (HR@1064 nm) are applied to an input facet facing the laser diode, and HR coating @1064 nm and AR coating @532 nm are applied to an output facet opposite to the input facet. When the lasing medium 104 and the intracavity frequency doubler 105 are discrete, AR coating @808 nm and HR coating @1064 nm and 532 nm are applied to the input facet of the lasing medium 104, and AR coating @1064 nm and 532 nm to an output facet of the lasing medium 104 opposite to the input facet thereof; while AR coating @1064 nm and 532 nm is applied to an input facet of the intracavity frequency doubler 105 facing the output facet of the lasing medium 104, and HR coating @1064 nm and an AR coating @532 are applied to an output facet of the intracavity frequency doubler 105 opposite to the input facet thereof.
The lasing medium 104 can be, most often, Nd:YAG or Nd:YVO4, or another crystal. The intracavity frequency doubler 105 is usually KTP, KDP, LBO, BBO, ADP, LiIO3, or another non-linear material that is able to efficiently produce an output that is twice the frequency of the signal applied to its input.
Generally, a focusing optics (also known as “circularizing optics”, must be inserted between the laser diode assembly and the optical resonant cavity for shaping the laser beam from the pump diode as round as possible.
An infrared (IR) blocking filter is provided in the path of the laser beam for removing the unwanted IR rays while providing excellent transmission for green wavelength. Optically, a Q-switch or a single mode device can also be inserted in the optical resonant cavity for making the laser into a pulse laser or a single longitudinal mode laser.
A photodiode is attached in the LD casing of the laser diode for receiving and sensing laser diode-generated pumping radiation and thus establishing a negative feedback for controlling the optical power output by the pump diode.
A photodiode is attached in the LD casing of the laser diode for receiving and sensing laser diode-generated pumping radiation and thus establishing a negative feedback for controlling the optical power output by the pump diode.
So, it is thought that if the optical resonant cavity, together with other wanted optics, can be put into within the casing of the laser diode before the semiconductor chip, the volume and weight of the whole DPSS laser will thus significantly minimized.